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The Trypanosoma cruzi nucleic acid binding protein Tc38 presents changes in the intramitochondrial distribution during the cell cycle.

Duhagon MA, Pastro L, Sotelo-Silveira JR, Pérez-Díaz L, Maugeri D, Nardelli SC, Schenkman S, Williams N, Dallagiovanna B, Garat B - BMC Microbiol. (2009)

Bottom Line: However, we found that Tc38 predominantly localizes into the mitochondrion.In epimastigotes, Tc38 is found only in association with kDNA in G1 phase.In non-replicating parasite stages such as trypomastigotes, the protein is found only surrounding the entire kinetoplast structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Montevideo, Uruguay. mduhagon@fcien.edu.uy

ABSTRACT

Background: Tc38 of Trypanosoma cruzi has been isolated as a single stranded DNA binding protein with high specificity for the poly [dT-dG] sequence. It is present only in Kinetoplastidae protozoa and its sequence lacks homology to known functional domains. Tc38 orthologues present in Trypanosoma brucei and Leishmania were proposed to participate in quite different cellular processes. To further understand the function of this protein in Trypanosoma cruzi, we examined its in vitro binding to biologically relevant [dT-dG] enriched sequences, its expression and subcellular localization during the cell cycle and through the parasite life stages.

Results: By using specific antibodies, we found that Tc38 protein from epimastigote extracts participates in complexes with the poly [dT-dG] probe as well as with the universal minicircle sequence (UMS), a related repeated sequence found in maxicircle DNA, and the telomeric repeat. However, we found that Tc38 predominantly localizes into the mitochondrion. Though Tc38 is constitutively expressed through non-replicating and replicating life stages of T. cruzi, its subcellular localization in the unique parasite mitochondrion changes according to the cell cycle stage. In epimastigotes, Tc38 is found only in association with kDNA in G1 phase. From the S to G2 phase the protein localizes in two defined and connected spots flanking the kDNA. These spots disappear in late G2 turning into a diffuse dotted signal which extends beyond the kinetoplast. This later pattern is more evident in mitosis and cytokinesis. Finally, late in cytokinesis Tc38 reacquires its association with the kinetoplast. In non-replicating parasite stages such as trypomastigotes, the protein is found only surrounding the entire kinetoplast structure.

Conclusions: The dynamics of Tc38 subcellular localization observed during the cell cycle and life stages support a major role for Tc38 related to kDNA replication and maintenance.

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Tc38 patterns in T. cruzi epimastigotes during the cell cycle. Phase contrast, DAPI staining and Tc38 signal are indicated. For the merge images, Tc38-Alexa 488 signal is shown in green and DAPI nucleic acid staining in blue. Selected parasites that show the most frequent patterns seen in the cell cycle phases are presented. A corresponds to G1/S, B to G2 and C to E show images from mitosis to cytokinesis. Each one of the Tc38 labeling patterns were found in the majority of examined cells (n ≥ 20). The arrow indicates the position of the second flagellum, indicative of G2. Black bars = 5 μm. The dotted lines in the phase contrast indicate the position enlarged in the fluorescent images. White bars = 2 μm.
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Figure 5: Tc38 patterns in T. cruzi epimastigotes during the cell cycle. Phase contrast, DAPI staining and Tc38 signal are indicated. For the merge images, Tc38-Alexa 488 signal is shown in green and DAPI nucleic acid staining in blue. Selected parasites that show the most frequent patterns seen in the cell cycle phases are presented. A corresponds to G1/S, B to G2 and C to E show images from mitosis to cytokinesis. Each one of the Tc38 labeling patterns were found in the majority of examined cells (n ≥ 20). The arrow indicates the position of the second flagellum, indicative of G2. Black bars = 5 μm. The dotted lines in the phase contrast indicate the position enlarged in the fluorescent images. White bars = 2 μm.

Mentions: For this purpose, we first analyzed asynchronic cultures. We based the identification of each cell cycle stage on morphological markers including both the number of nuclei and kinetoplasts determined by DAPI staining together with the number and appearance of flagella assessed by phase contrast microscopy [25]. Figure 5 shows the sequential changes in Tc38 localization during the cell cycle. It shows that G1/S cells usually exhibit a homogeneous signal over the kDNA (Figure 5A) even though in some cases Tc38 condenses in two small antipodal sites. Cells at G2 (see arrow showing the second flagellum in phase contrast image) exhibit a diffuse signal connecting what now has become two clearly defined spots (Figure 5B). The two Tc38 spot signals do not seem to exactly co-localize with the DAPI staining. As the cell cycle progresses the defined spots of Tc38 disappear and the diffuse dotted signal spreads out, covering a region far beyond the kinetoplast and without an evident association with it (Figure 5C and 5D). Finally in late cytokinesis the signal of Tc38 tends to regain the homogenous distribution over the kDNA (Figure 5E).


The Trypanosoma cruzi nucleic acid binding protein Tc38 presents changes in the intramitochondrial distribution during the cell cycle.

Duhagon MA, Pastro L, Sotelo-Silveira JR, Pérez-Díaz L, Maugeri D, Nardelli SC, Schenkman S, Williams N, Dallagiovanna B, Garat B - BMC Microbiol. (2009)

Tc38 patterns in T. cruzi epimastigotes during the cell cycle. Phase contrast, DAPI staining and Tc38 signal are indicated. For the merge images, Tc38-Alexa 488 signal is shown in green and DAPI nucleic acid staining in blue. Selected parasites that show the most frequent patterns seen in the cell cycle phases are presented. A corresponds to G1/S, B to G2 and C to E show images from mitosis to cytokinesis. Each one of the Tc38 labeling patterns were found in the majority of examined cells (n ≥ 20). The arrow indicates the position of the second flagellum, indicative of G2. Black bars = 5 μm. The dotted lines in the phase contrast indicate the position enlarged in the fluorescent images. White bars = 2 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2654453&req=5

Figure 5: Tc38 patterns in T. cruzi epimastigotes during the cell cycle. Phase contrast, DAPI staining and Tc38 signal are indicated. For the merge images, Tc38-Alexa 488 signal is shown in green and DAPI nucleic acid staining in blue. Selected parasites that show the most frequent patterns seen in the cell cycle phases are presented. A corresponds to G1/S, B to G2 and C to E show images from mitosis to cytokinesis. Each one of the Tc38 labeling patterns were found in the majority of examined cells (n ≥ 20). The arrow indicates the position of the second flagellum, indicative of G2. Black bars = 5 μm. The dotted lines in the phase contrast indicate the position enlarged in the fluorescent images. White bars = 2 μm.
Mentions: For this purpose, we first analyzed asynchronic cultures. We based the identification of each cell cycle stage on morphological markers including both the number of nuclei and kinetoplasts determined by DAPI staining together with the number and appearance of flagella assessed by phase contrast microscopy [25]. Figure 5 shows the sequential changes in Tc38 localization during the cell cycle. It shows that G1/S cells usually exhibit a homogeneous signal over the kDNA (Figure 5A) even though in some cases Tc38 condenses in two small antipodal sites. Cells at G2 (see arrow showing the second flagellum in phase contrast image) exhibit a diffuse signal connecting what now has become two clearly defined spots (Figure 5B). The two Tc38 spot signals do not seem to exactly co-localize with the DAPI staining. As the cell cycle progresses the defined spots of Tc38 disappear and the diffuse dotted signal spreads out, covering a region far beyond the kinetoplast and without an evident association with it (Figure 5C and 5D). Finally in late cytokinesis the signal of Tc38 tends to regain the homogenous distribution over the kDNA (Figure 5E).

Bottom Line: However, we found that Tc38 predominantly localizes into the mitochondrion.In epimastigotes, Tc38 is found only in association with kDNA in G1 phase.In non-replicating parasite stages such as trypomastigotes, the protein is found only surrounding the entire kinetoplast structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Montevideo, Uruguay. mduhagon@fcien.edu.uy

ABSTRACT

Background: Tc38 of Trypanosoma cruzi has been isolated as a single stranded DNA binding protein with high specificity for the poly [dT-dG] sequence. It is present only in Kinetoplastidae protozoa and its sequence lacks homology to known functional domains. Tc38 orthologues present in Trypanosoma brucei and Leishmania were proposed to participate in quite different cellular processes. To further understand the function of this protein in Trypanosoma cruzi, we examined its in vitro binding to biologically relevant [dT-dG] enriched sequences, its expression and subcellular localization during the cell cycle and through the parasite life stages.

Results: By using specific antibodies, we found that Tc38 protein from epimastigote extracts participates in complexes with the poly [dT-dG] probe as well as with the universal minicircle sequence (UMS), a related repeated sequence found in maxicircle DNA, and the telomeric repeat. However, we found that Tc38 predominantly localizes into the mitochondrion. Though Tc38 is constitutively expressed through non-replicating and replicating life stages of T. cruzi, its subcellular localization in the unique parasite mitochondrion changes according to the cell cycle stage. In epimastigotes, Tc38 is found only in association with kDNA in G1 phase. From the S to G2 phase the protein localizes in two defined and connected spots flanking the kDNA. These spots disappear in late G2 turning into a diffuse dotted signal which extends beyond the kinetoplast. This later pattern is more evident in mitosis and cytokinesis. Finally, late in cytokinesis Tc38 reacquires its association with the kinetoplast. In non-replicating parasite stages such as trypomastigotes, the protein is found only surrounding the entire kinetoplast structure.

Conclusions: The dynamics of Tc38 subcellular localization observed during the cell cycle and life stages support a major role for Tc38 related to kDNA replication and maintenance.

Show MeSH
Related in: MedlinePlus